This invention relates to an improved control system for controlling the position of a crop discharge spout on an agricultural machine having a crop-receiving wagon pivotally attached thereto.
Automatic systems have been proposed to automatically control forage harvester spout position to prevent crop spillage. One such system is described in U.S. Pat. No. 3,786,945. The '945 system is complicated in that it requires an excitation signal generator and transmitter, signal coils and a phase detector. Another automatic system, which includes light-emitting diodes and photo transistors, is described in U.S. Pat. No. 4,042,132. Both systems provide for accurate tracking of the spout to within a narrow angle range with respect to the crop-receiving wagon when turns are being executed. However, neither system automatically provides for a wider amount of free play between the spout and the wagon during straight line travel so that the operator can manually control the spout to obtain uniform wagon filling while the automatic control system is still operative as a backup. The '132 patent discloses a mechanical idler, but this mechanical idler provides free play only between the wagon and the wagon-machine angle sensor and thus reduces the sensitivity of the wagon-machine angle sensor. This prevents the '132 control system from moving the spout to make the spout-wagon misalignment less than the amount of free play provided by the mechanical idler. Furthermore, the free play provided by the mechanical idler does not vary according to the wagon-machine angle. Instead, the idler free play is constant over all wagon-machine angles. Finally, in order to change between the manual and automatic control modes, the operator of the '132 system is required to first actuate a mode select switch.